A process for making spun fleece or nonwoven mat from endless synthetic resin filament using a filament-spinning unit is known. The filament-spinning unit includes a spinning nozzle system, a cooling shaft, a stretching aperture, a diffuser shaft, a continuously moving fleece recovery conveyor and a device for feeding process air and for drawing outflowing air through the fleece recovery conveyor. The cooling shaft has a shaft wall provided with a plurality of air orifices and process air required for cooling is admitted through the air orifices to provide an air flow. The air flow is at least partially drawn through the fleece recovery conveyor.
According to the features of the known filament-spinning unit, the process parameters such as the flow rate of thermoplastic material, process air, the transport speed of the fleece recovery conveyor and the geometric parameters of the filament-spinning unit are set up so that the spun fleece is produced with as exact and as uniform a given thickness as possible. In other words it has a preset surface or area weight. However in the existing process and/or in the existing filament-spinning unit it is not possible to successfully correct or even control thickness deviations from a uniform thickness. The thickness deviations have up to now been considered as intrinsic to the system.